JPH0699163B2 - Vitrification method of optical fiber base material - Google Patents

Vitrification method of optical fiber base material

Info

Publication number
JPH0699163B2
JPH0699163B2 JP60168035A JP16803585A JPH0699163B2 JP H0699163 B2 JPH0699163 B2 JP H0699163B2 JP 60168035 A JP60168035 A JP 60168035A JP 16803585 A JP16803585 A JP 16803585A JP H0699163 B2 JPH0699163 B2 JP H0699163B2
Authority
JP
Japan
Prior art keywords
base material
porous glass
glass base
vitrification
germanium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP60168035A
Other languages
Japanese (ja)
Other versions
JPS6230636A (en
Inventor
健之 菊池
保 神谷
高野　　博
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
THE FURUKAW ELECTRIC CO., LTD.
Original Assignee
THE FURUKAW ELECTRIC CO., LTD.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by THE FURUKAW ELECTRIC CO., LTD. filed Critical THE FURUKAW ELECTRIC CO., LTD.
Priority to JP60168035A priority Critical patent/JPH0699163B2/en
Publication of JPS6230636A publication Critical patent/JPS6230636A/en
Publication of JPH0699163B2 publication Critical patent/JPH0699163B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/01446—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
    • C03B2201/31—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with germanium

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Thermal Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Glass Melting And Manufacturing (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Description

【発明の詳細な説明】 〔技術分野〕 本発明はVAD法により合成したゲルマニウムをドープし
てなる多孔質ガラス母材をガラス化するに際し、該多孔
質ガラス母材の外周部に長手方向に均一な厚さを有する
クラッド層を形成する光フアイバ母材のガラス化方法に
関するものである。Description: TECHNICAL FIELD The present invention relates to the vitrification of a porous glass base material obtained by doping germanium synthesized by a VAD method, and uniformly in the longitudinal direction on the outer peripheral portion of the porous glass base material. The present invention relates to a vitrification method for an optical fiber preform for forming a clad layer having a uniform thickness.

〔従来技術〕[Prior art]

コア及び該コアのまわりに該コアより屈折率の低いクラ
ッド層を有する光フアイバ母材を製造する一つの方法と
して、まずゲルマニウム（ガラスの屈折率を高めるドー
プ材料）をドープしてなる多孔質ガラス母材を既知のVA
D法により合成し、これを塩素を含む雰囲気で加熱し透
明ガラス化し、該透明ガラス化時に下記の反応により前
記多孔質ガラス母材の表面からゲルマニウムを揮散させ
クラッド層を形成する方法が従来から試みられている。
この反応とは以下の通りである。As one method for producing an optical fiber preform having a core and a clad layer having a refractive index lower than that of the core around the core, a porous glass obtained by first doping germanium (a doping material for increasing the refractive index of glass). Base material known VA
Synthesized by the method D, heating it in an atmosphere containing chlorine to form a transparent glass, and a method of forming a clad layer by volatilizing germanium from the surface of the porous glass base material by the following reaction during the transparent vitrification is conventional Being tried.
This reaction is as follows.

GeO2＋２Cl2→GeCl4＋O2……（１） （１）の反応により多孔質ガラス母材のガラス化と、ゲ
ルマニウムの揮散によるクラッド層の形成と、さらには
塩素の脱水効果により多孔質ガラス母材からの脱水も同
時に行なう。しかしながらこの方法では第３図（ロ）に
示す如くコアの周辺に裾引き８、８ができて明確なクラ
ッド層ができにくい。GeO 2 + 2Cl 2 → GeCl 4 + O 2 (1) (1) Vitrification of the porous glass base material by the reaction, formation of a clad layer by volatilization of germanium, and further porous glass by the chlorine dehydration effect. Dehydration from the base material is also performed at the same time. However, in this method, as shown in FIG. 3B, the bottoms 8 are formed around the core, and it is difficult to form a clear cladding layer.

そこで、本発明者等は塩素の代わりに酸素をキャリアガ
スとする塩化チオニルを含む雰囲気下で前記多孔質ガラ
ス母材の脱水、ゲルマニウムの揮散によるクラッド層の
形成を試みた。結果を第３図（イ）に示すようにクラッ
ド層を作ることができなかった。Therefore, the present inventors tried to form a clad layer by dehydrating the porous glass base material and volatilizing germanium in an atmosphere containing thionyl chloride using oxygen as a carrier gas instead of chlorine. As a result, as shown in FIG. 3 (a), the clad layer could not be formed.

そこでさらに不活性ガス、例えばHe、Ar、N2等をキャリ
アガスとする塩化チオニルを含む雰囲気で前記多孔質ガ
ラス母材の脱水、ゲルマニウムの揮散を行った。この方
法では第３図（ハ）のようにコア１のまわりに明確なク
ラッド層２は形成できたものの、前記多孔質ガラス母材
の長手方向のガラス化時の熱履歴が異なるため（加熱炉
内の温度分布が均一でないこと等に起因する）、ガラス
化による多孔質ガラス母材の粒子表面積の減少速度が母
材の長手方向において一定とならず、すなわち、前記
（１）の反応が完了するまでの時間が前記母材の長手方
向に一定でないため、長手方向に均一な厚さのクラッド
層を形成するには至らなかった。Therefore, the porous glass base material was dehydrated and germanium was volatilized in an atmosphere containing thionyl chloride with an inert gas such as He, Ar, and N 2 as a carrier gas. Although a clear clad layer 2 could be formed around the core 1 by this method as shown in FIG. 3C, since the heat history during vitrification in the longitudinal direction of the porous glass base material is different (heating furnace Due to non-uniform temperature distribution in the interior), the rate of decrease of the particle surface area of the porous glass preform due to vitrification is not constant in the longitudinal direction of the preform, that is, the reaction of (1) above is completed. Since the time until it was formed was not constant in the longitudinal direction of the base material, it was not possible to form a clad layer having a uniform thickness in the longitudinal direction.

このように従来においては、VAD法により合成したゲル
マニウムをドープしてなる多孔質ガラス母材を、ガラス
化と同時に該多孔質ガラス母材の外周部からゲルマニウ
ムを揮散させクラッド層を形成しようという試みはあっ
ても成功には至っていない。Thus, in the conventional case, an attempt was made to form a clad layer by volatilizing germanium from the outer peripheral portion of the porous glass base material at the same time as vitrifying the porous glass base material doped with germanium synthesized by the VAD method. Even so, it has not been successful.

〔発明の目的〕[Object of the Invention]

前記問題に鑑み本発明の目的は、VAD法により合成して
なるゲルマニウム入り多孔質ガラス母材を透明ガラス化
するに際し、該透明ガラス化と同時に前記多孔質ガラス
母材の外周部からゲルマニウムを揮散せしめ、前記多孔
質ガラス母材の外周部に長手方向に均一な厚さのクラッ
ド層を容易に形成できる方法を提供することにある。In view of the above problems, an object of the present invention is to transparentize vitrification of a germanium-containing porous glass base material synthesized by the VAD method, and volatilize germanium from the outer periphery of the porous glass base material simultaneously with the transparent vitrification. At the very least, it is to provide a method capable of easily forming a clad layer having a uniform thickness in the longitudinal direction on the outer peripheral portion of the porous glass base material.

〔発明の構成〕[Structure of Invention]

前記目的を達成すべく本発明は、VAD法により合成した
ゲルマニウムをドープしてなる多孔質ガラス母材を塩化
物を含む無酸素雰囲気でガラス化して、該ガラス化によ
り前記多孔質ガラス母材の外周部から前記ゲルマニウム
を揮散させて前記多孔質ガラス母材の外周部に長手方向
に均一なクラッド層を形成する光フアイバ母材のガラス
化方法において、前記ガラス化に先立ち前記塩化物を含
む無酸素雰囲気とは異なる雰囲気で前記多孔質ガラス母
材を予備加熱してその収縮率を0.1〜0.7にせしめ、しか
る後前記塩化物を含む無酸素雰囲気でガラス化すること
を特徴とするものである。In order to achieve the above-mentioned object, the present invention is a vitrification of a germanium-doped porous glass base material synthesized by the VAD method in an oxygen-free atmosphere containing chloride, and the vitrification of the porous glass base material In the vitrification method of an optical fiber preform in which the germanium is volatilized from the outer periphery to form a uniform clad layer in the longitudinal direction on the outer periphery of the porous glass preform, prior to the vitrification, no chloride is contained. The porous glass base material is preheated in an atmosphere different from the oxygen atmosphere so that the shrinkage ratio is 0.1 to 0.7, and then vitrified in an oxygen-free atmosphere containing the chloride. .

〔発明の実施例〕Example of Invention

本発明の実施例を図を参照して詳細に説明する。本発明
においては、まずゲルマニウム（ガラスの屈折率を高め
る材料）をドープしてなる多孔質ガラス母材３をVAD法
により合成する。これを抵抗加熱炉４に囲まれてなる石
英製の炉心管５に挿入し、後述するガラス化雰囲気とは
異なる雰囲気で、具体的には、塩化物を含む無酸素雰囲
気とは異なる雰囲気で、この多孔質ガラス母材の外周部
からゲルマニウムの揮散を抑制しつつ、かつこの多孔質
ガラス母材３がガラス化しないように注意しながら予備
加熱し、ガラス化後の密度に対してその密度の比が0.1
〜0.7になるように収縮せしめる。ここで前記比を収縮
率と呼ぶことにし次のように定義する。Embodiments of the present invention will be described in detail with reference to the drawings. In the present invention, first, the porous glass base material 3 doped with germanium (a material for increasing the refractive index of glass) is synthesized by the VAD method. This is inserted into a quartz core tube 5 surrounded by a resistance heating furnace 4, and in an atmosphere different from a vitrification atmosphere described later, specifically, in an atmosphere different from an oxygen-free atmosphere containing chloride, Preheating is performed while suppressing volatilization of germanium from the outer peripheral portion of the porous glass base material and being careful not to vitrify the porous glass base material 3. Ratio is 0.1
Shrink to ~ 0.7. Here, the above-mentioned ratio is called a shrinkage rate and is defined as follows.

収縮率＝加熱収縮後の密度／ガラス化後の密度 尚、多孔質ガラス母材３を前記の如く収縮するにあた
り、炉心管５の中にはヘリウム、酸素及び塩化チオニル
を流し多孔質ガラス母材３から脱泡、脱水を行ってもよ
いが、この予備加熱工程では前記ガスによる雰囲気は不
可欠の条件ではない。但し、この予備加熱工程中では、
多孔質ガラス母材３の外周部からのゲルマニウムの揮散
をできるだけ抑えることが必要である。このようにして
多孔質ガラス母材３を収縮率0.1〜0.7の範囲に収縮せし
めたら、次にこれをヘリウムと、塩化チオニル等の塩化
物を含む無酸素雰囲気の炉心管５内で前記抵抗加熱炉３
により約1400℃に加熱して透明ガラス化する。Shrinkage = Density after heat shrinkage / Density after vitrification Incidentally, when shrinking the porous glass base material 3 as described above, helium, oxygen and thionyl chloride are caused to flow into the furnace tube 5 to make the porous glass base material. Although defoaming and dehydration may be performed from No. 3, the atmosphere by the gas is not an essential condition in this preheating step. However, during this preheating step,
It is necessary to suppress the volatilization of germanium from the outer peripheral portion of the porous glass base material 3 as much as possible. After shrinking the porous glass base material 3 in the range of 0.1 to 0.7, the resistance heating is performed in the oxygen-free atmosphere of the furnace core tube 5 containing helium and chloride such as thionyl chloride. Furnace 3
By heating to about 1400 ℃, it becomes transparent glass.

このようにゲルマニウムをドープしてなる多孔質ガラス
母材３を塩化物を含む無酸素雰囲気で透明ガラス化する
前に予備加熱してその収縮率を0.1〜0.7にせしめると、
該多孔質ガラス母材３から脱水が充分行われると同時
に、多孔質ガラス母材３の外周部に該多孔質ガラス母材
３の長手方向にわたって均一な厚さを有する明確なるク
ラッド層２を形成することができた。その理由は本発明
にあっては予め多孔質ガラス母材３を収縮したがために
還元作用を有する塩化物が、前記多孔質ガラス母材３内
に収縮前の多孔質ガラス母材３に対してより入り込みに
くくなり、その結果前述した（１）の反応がゆるやかに
行われ、さらに既に収縮が前工程である程度進んでいる
ため、透明ガラス化が速やかに進行する。すなわち、前
述した（１）の反応が多孔質ガラス母材３の長手方向に
一定速度で進行し、もってこの反応の停止が均一に完了
する。その結果仮に多孔質ガラス母材３にあってガラス
化時その長手方向に多少の熱履歴の相違等があっても長
手方向に均一なるクラッド層２が形成できるものと推定
される。これに対して従来の方法にあっては、多孔質ガ
ラス母材３がなんら収縮していないため塩化物が急激に
前記多孔質ガラス母材３内に取り込まれ、前記（１）の
反応が急激に起こり、この反応の完了までの時間やその
度合が多孔質ガラス母材３の長手方向において異なる。
その結果母材長手方向のゲルマニウムの揮散にばらつき
が生じ、均一なるクラッド層２を作ることができない、
と考えられる。尚、VAD法により多孔質ガラス母材３を
合成する際、堆積面温度を高めると予め収縮した多孔質
ガラス母材３を得ることができるが、この方法では良好
な屈折率分布が得られず不適であった。As described above, when the porous glass base material 3 doped with germanium is preheated in the oxygen-free atmosphere containing chloride before being vitrified, the shrinkage ratio is set to 0.1 to 0.7.
The porous glass base material 3 is sufficiently dehydrated, and at the same time, a clear clad layer 2 having a uniform thickness is formed on the outer peripheral portion of the porous glass base material 3 in the longitudinal direction of the porous glass base material 3. We were able to. The reason is that, in the present invention, the chloride having a reducing action because the porous glass base material 3 has been contracted in advance has a reducing action in the porous glass base material 3 relative to the porous glass base material 3 before contraction. As a result, the reaction (1) described above is carried out slowly, and since the shrinkage has already progressed to some extent in the previous step, transparent vitrification proceeds rapidly. That is, the above-described reaction (1) proceeds at a constant speed in the longitudinal direction of the porous glass base material 3, so that the termination of this reaction is uniformly completed. As a result, it is presumed that even if the porous glass base material 3 is vitrified and there is a slight difference in the heat history in the longitudinal direction, the clad layer 2 that is uniform in the longitudinal direction can be formed. On the other hand, in the conventional method, since the porous glass base material 3 has not shrunk at all, chloride is rapidly taken into the porous glass base material 3 and the reaction (1) is rapidly performed. Occurs in the longitudinal direction of the porous glass base material 3 and the time to completion of this reaction varies.
As a result, volatilization of germanium in the longitudinal direction of the base material varies, and it is not possible to form a uniform clad layer 2.
it is conceivable that. In addition, when synthesizing the porous glass base material 3 by the VAD method, it is possible to obtain the porous glass base material 3 that has been contracted in advance by increasing the deposition surface temperature, but this method does not provide a good refractive index distribution. It was unsuitable.

以下に本発明の具体例を示す。尚使用したゲルマニウム
ドープド多孔質ガラス母材３はすべて既知のVAD法によ
り合成したものである。Specific examples of the present invention are shown below. The germanium-doped porous glass base materials 3 used were all synthesized by the known VAD method.

具体例−１ 前記多孔質ガラス母材３をまず炉内最高温度が1300〜15
00℃（適温は約1400℃）でその前後に適当な温度分布を
有する抵抗加熱炉４により囲まれた石英製の炉心管５内
に毎分100〜1000mm/min（最適値700mm/min）の速さで一
度昇降させ、前記多孔質ガラス母材３の収縮率を0.4に
せしめた。ここで前記炉心管５内にはヘリウム、塩化チ
オニルおよび酸素を流しておいたが、これらガスは無く
てもよいが、予め脱水処理を行っておく意味からあった
方が好ましい。尚、前記の如くヘリウムと塩化チオニル
を流す場合には、多孔質ガラス母材３中のゲルマニウム
が塩化物となって多孔質ガラス母材３の外周部から揮散
するのを防止すべく酸素は不可欠である。その理由は、
酸素の存在がゲルマニウムの塩化物化を阻止するからで
ある。Specific Example-1 First, the maximum temperature in the furnace of the porous glass base material 3 is 1300 to 15
100 to 1000 mm / min (optimal value 700 mm / min) in a quartz core tube 5 surrounded by a resistance heating furnace 4 having an appropriate temperature distribution before and after 00 ° C (suitable temperature is about 1400 ° C). It was moved up and down once at a speed so that the shrinkage ratio of the porous glass base material 3 was 0.4. Here, helium, thionyl chloride, and oxygen were made to flow in the core tube 5, but these gases may be omitted, but it is preferable to perform dehydration treatment in advance. When flowing helium and thionyl chloride as described above, oxygen is indispensable to prevent germanium in the porous glass base material 3 from becoming a chloride and volatilizing from the outer peripheral portion of the porous glass base material 3. Is. The reason is,
This is because the presence of oxygen prevents chlorination of germanium.

このように多孔質ガラス母材３を収縮せしめたらこれを
前記炉心管５内に再度180mm/minの速度で下降せしめて
透明ガラス化した。このとき前記炉心管５内にはヘリウ
ム40l/min、塩化チオニル0.5l/minを流しておいた。こ
のようにして得た光フアイバ母材におけるクラッド外径
／コア外径の比率を前記光フアイバ母材の長手方向にわ
たって調べたら第１図の○印で示す如く長手方向に均一
な分布になった。When the porous glass preform 3 was contracted in this way, it was again lowered into the core tube 5 at a speed of 180 mm / min to form a transparent glass. At this time, 40 l / min of helium and 0.5 l / min of thionyl chloride were flown into the core tube 5. When the ratio of the clad outer diameter / core outer diameter in the optical fiber preform thus obtained was examined in the longitudinal direction of the optical fiber preform, it was found to have a uniform distribution in the longitudinal direction as shown by the circles in FIG. .

具体例−２ 前記多孔質ガラス母材３をまず炉内最高温度を約1100℃
に設定した抵抗加熱炉４により囲まれた石英製の炉心管
５内で予備加熱してその収縮率を0.7にせしめた。ここ
で前記炉心管５内にはなんらガスは流さなかった。Example-2 The porous glass base material 3 is first heated to a maximum temperature of about 1100 ° C in the furnace.
In the quartz furnace core tube 5 surrounded by the resistance heating furnace 4 set to 1, the shrinkage rate was set to 0.7. Here, no gas was flown into the core tube 5.

このようにして多孔質ガラス母材３を収縮せしめたらこ
れを炉内最高温度を約1400℃に設定した前記炉心管５内
に150mm/minの速度で下降せしめて透明ガラス化した。
このとき前記炉心管５内は前記具体例−１と同様に無酸
素雰囲気とし、かつヘリウム40l/min、塩化チオニル0.5
l/minを流しておいた。このようにして得た光フアイバ
母材におけるクラッド外径／コア外径の比率を前記光フ
アイバ母材の長手方向にわたって調べたら第１図の□印
で示すごとく長手方向に均一な分布になった。When the porous glass preform 3 was contracted in this manner, it was lowered into the furnace core tube 5 in which the maximum temperature in the furnace was set to about 1400 ° C. at a speed of 150 mm / min to obtain transparent vitrification.
At this time, the inside of the furnace tube 5 was made an oxygen-free atmosphere in the same manner as in Concrete Example 1, and helium 40 l / min and thionyl chloride 0.5
l / min was passed. When the ratio of the clad outer diameter / core outer diameter in the optical fiber preform thus obtained was examined over the longitudinal direction of the optical fiber preform, a uniform distribution was obtained in the longitudinal direction as shown by □ in FIG. .

尚、前記具体例−１及び具体例−２における予備加熱方
法の他にも、例えばVAD法により多孔質ガラス母材３を
形成する際に合成用バーナの上段に予備加熱用のバーナ
を設け、多孔質ガラス母材３の合成と予備加熱を同時に
行う方法もある。また予備加熱用の加熱炉４と透明ガラ
ス化用加熱炉４を別個に設けて各々を別工程でやっても
よい。さらに加熱炉としては本実施例の抵抗加熱炉４以
外にも高周波加熱炉、カーボン加熱炉又はシリコニット
加熱炉等が使用できる。In addition to the preheating method in the specific example-1 and the specific example-2, for example, when the porous glass base material 3 is formed by the VAD method, a preheating burner is provided in the upper stage of the synthesis burner, There is also a method of simultaneously synthesizing the porous glass base material 3 and preheating it. Further, the heating furnace 4 for preheating and the heating furnace 4 for transparent vitrification may be separately provided and each may be performed in a separate step. Further, as the heating furnace, in addition to the resistance heating furnace 4 of this embodiment, a high frequency heating furnace, a carbon heating furnace, a silicon knit heating furnace, or the like can be used.

また多孔質ガラス母材３の収縮率を0.1〜0.7に限定する
理由は、0.7より大きいと、多孔質ガラス母材３の一部
が焼結してしまい、その結果塩化物が多孔質ガラス母材
３の中に入っていくことができず、第１図の▲印のよう
にクラッド層２の形成がほとんどできなくなる。つまり
ゲルマニウムの揮散もさらには脱水も行うことができな
くなる。一方収縮率が0.1だと第１図の☆印の如くまだ
かなり安定した厚さのクラッド層２を形成できるが、0.
05になると第１図の△印が示すように多孔質ガラス母材
３のガラス化時の熱履歴が一般に安定しない母材両端部
で均一な厚さのクラッド層２を形成できない。つまり収
縮率が0.1未満になると多孔質ガラス母材３内に塩化物
のガスが急激に入ってしまい、前述の（１）の反応の完
了までの時間や度合が不安定で、形成されるクラッド層
２の厚さは母材３の長手方向に均一にならない。The reason why the shrinkage ratio of the porous glass base material 3 is limited to 0.1 to 0.7 is that if it is larger than 0.7, a part of the porous glass base material 3 will be sintered, and as a result, chloride will be contained in the porous glass base material 3. The material cannot enter the material 3, and the clad layer 2 can hardly be formed as indicated by the mark ∘ in FIG. In other words, neither volatilization of germanium nor dehydration is possible. On the other hand, if the shrinkage ratio is 0.1, the clad layer 2 having a fairly stable thickness can be formed as shown by the star mark in Fig. 1, but
At 05, the heat history during vitrification of the porous glass base material 3 is generally not stable as shown by the triangle mark in FIG. 1, and it is not possible to form the clad layer 2 having a uniform thickness at both ends of the base material. In other words, when the shrinkage ratio is less than 0.1, chloride gas rapidly enters the porous glass base material 3, and the time and degree to completion of the above reaction (1) are unstable, and the clad formed The thickness of the layer 2 is not uniform in the longitudinal direction of the base material 3.

〔発明の効果〕〔The invention's effect〕

前述の如く本発明によれば、VAD法により合成されてな
るゲルマニウム入り多孔質ガラス母材を透明ガラス化す
るに際し、該透明ガラス化と同時に前記多孔質ガラス母
材の外周部からゲルマニウムを揮散せしめ、前記多孔質
ガラス母材の外周部に長手方向に均一なクラッド層を容
易に形成できる。As described above, according to the present invention, when vitrifying the germanium-containing porous glass base material synthesized by the VAD method, the germanium is volatilized from the outer peripheral portion of the porous glass base material at the same time as the transparent vitrification. A clad layer that is uniform in the longitudinal direction can be easily formed on the outer peripheral portion of the porous glass preform.

【図面の簡単な説明】[Brief description of drawings]

第１図は本発明で得られた光フアイバ母材及び比較例と
して挙げた光フアイバ母材のクラッド層の厚さ／コアの
半径の比を長手方向に調査した結果を示すグラフ、第２
図は本発明により多孔質ガラス母材を予備加熱する装置
の一実施例を示す概略図、第３図は従来方法により得ら
れる各光フアイバ母材の屈折率分布を示すグラフであ
る。 １〜コア、２〜クラッド層、３〜多孔質ガラス母材、４
〜抵抗加熱炉、５〜炉心管FIG. 1 is a graph showing the results of longitudinal examination of the ratio of the clad layer thickness / core radius of the optical fiber base material obtained in the present invention and the optical fiber base material given as a comparative example.
FIG. 3 is a schematic view showing an embodiment of an apparatus for preheating a porous glass preform according to the present invention, and FIG. 3 is a graph showing a refractive index distribution of each optical fiber preform obtained by a conventional method. 1-core, 2-cladding layer, 3-porous glass base material, 4
~ Resistance heating furnace, 5 ~ Core tube

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】VAD法により合成したゲルマニウムをドー
プしてなる多孔質ガラス母材を塩化物を含む無酸素雰囲
気でガラス化して、該ガラス化により前記多孔質ガラス
母材の外周部から前記ゲルマニウムを揮散させて前記多
孔質ガラス母材の外周部に長手方向に均一なクラッド層
を形成する光フアイバ母材のガラス化方法において、前
記ガラス化に先立ち前記塩化物を含む無酸素雰囲気とは
異なる雰囲気で前記多孔質ガラス母材を予備加熱してそ
の収縮率を0.1〜0.7にせしめ、しかる後前記塩化物を含
む無酸素雰囲気でガラス化することを特徴とする光フア
イバ母材のガラス化方法。1. A germanium-doped porous glass base material synthesized by the VAD method is vitrified in an oxygen-free atmosphere containing chloride, and the germanium is introduced from the outer peripheral portion of the porous glass base material by vitrification. In the vitrification method of the optical fiber preform, which volatilizes to form a uniform clad layer in the longitudinal direction on the outer peripheral portion of the porous glass preform, different from the oxygen-free atmosphere containing the chloride prior to the vitrification. A method for vitrifying an optical fiber preform, characterized in that the porous glass preform is preheated in an atmosphere so that its shrinkage is 0.1 to 0.7, and then vitrified in an oxygen-free atmosphere containing the chloride. .
JP60168035A 1985-07-30 1985-07-30 Vitrification method of optical fiber base material Expired - Fee Related JPH0699163B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP60168035A JPH0699163B2 (en) 1985-07-30 1985-07-30 Vitrification method of optical fiber base material

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP60168035A JPH0699163B2 (en) 1985-07-30 1985-07-30 Vitrification method of optical fiber base material

Publications (2)

Publication Number Publication Date
JPS6230636A JPS6230636A (en) 1987-02-09
JPH0699163B2 true JPH0699163B2 (en) 1994-12-07

Family

ID=15860609

Family Applications (1)

Application Number Title Priority Date Filing Date
JP60168035A Expired - Fee Related JPH0699163B2 (en) 1985-07-30 1985-07-30 Vitrification method of optical fiber base material

Country Status (1)

Country Link
JP (1) JPH0699163B2 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6272536A (en) * 1985-09-25 1987-04-03 Asahi Glass Co Ltd Production of high-purity quartz glass
JPS6283325A (en) * 1985-10-08 1987-04-16 Asahi Glass Co Ltd Production of quartz glass having high purity
JPH0631982B2 (en) * 1988-09-30 1994-04-27 カシオ計算機株式会社 Automatic rhythm accompaniment device
DE3911745A1 (en) * 1989-04-11 1990-10-25 Philips Patentverwaltung METHOD FOR PRODUCING GLASS BODIES WITH AREAS OF DIFFERENT OPTICAL BREAKAGE
JP7024489B2 (en) * 2018-02-21 2022-02-24 住友電気工業株式会社 Manufacturing method of base material for optical fiber

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5973443A (en) * 1982-10-18 1984-04-25 Sumitomo Electric Ind Ltd Manufacture of glass proform for optical fiber

Also Published As

Publication number Publication date
JPS6230636A (en) 1987-02-09

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